1. Field of the Invention
The present invention generally relates to a liquid crystal display device, and more particularly relates to a thin film transistor (TFT) array substrate for the liquid crystal display device and the manufacturing method thereof.
2. Description of the Prior Art
FIG. 1 is illustrated a plane view of the liquid crystal display according to the prior art. Referring to FIG. 1, scan lines 102 and source lines 109 are disposed to cross to define a plurality of pixel regions. The storage capacitance line (Cs line) 104 is extended over the pixel region to cross the source line 109. An omhic contact thin film 106, a source electrode 110 and a drain electrode 111 are disposed on the scan line 102. Besides, a pixel electrode 114 is disposed in the pixel region. Wherein, scan lines 102 and the Cs lines 104 are simultaneously formed and there is an insulating layer, not shown in the figure, covered thereon. The Cs line 104 is electrically isolated by the insulating layer and is under crossing the source line 109.
Due to the fact that the complex metal is used, it is difficult to control a good profile of the taper angle because of the etching rate of different materials so as to easily cause the undercut effect. Such as shown in FIG. 2, it is the sectional view of the A-A′ cross-section of FIG. 1 at the cross portion of the source line 109 and the storage capacitance line 104, the undercut effect presents at the Cs line 104 of the first metal layer arranged on a substrate 100. An insulating layer 103 is formed on the Cs line 104 of the first metal layer and then a source line 109 of a second metal layer is formed on the Cs line 104 of the first metal layer. Because of the undercut effect of the first metal layer, it easily causes the rip of the insulating layer 103 so as to occur the short of the source line 109 and the Cs line 104. This defect will cause the light line of the liquid crystal display device while turning on the panel and this panel must perform the array test to find the defect and perform the laser repair. Further, the panel is scrapping. Hence, how to overcome the mentioned problem is important for enhancing the yield of the LCD panel.